Staff at a Merseyside-based company have been told their salaries will be frozen indefinitely unless they agree to axe future increases to pensions.

Union Unite said Pilkington Glass staff were ready to strike over attempts to "bully and intimidate" them.

The St Helens-based firm told staff their pensionable salary will be fixed at their pay level as of April 2013.

If they do not agree they will get no further pay increases, a letter to employees said.

Linda McCulloch, of Unite, said: "The owner of Pilkington Glass is attempting to bully and intimidate staff out of their hard-earned pensions.

"The company has refused to negotiate or explore alternatives to freezing its workers' pensionable pay.

"Staff are furious, nine in ten of them want a strike ballot plus the union is taking advice from its lawyers on the legality of the company's proposals."

In the letter to staff Mark Lyons, chief financial officer, wrote: "The company has explained to the Pilkington Superannuation Scheme (PSS) membership the financial position of both the company and the PSS and hopes that members of the PSS will accept that the change is a sensible and responsible course of action in order to protect the company and PSS alike."

Pilkington Glass, which employs 1,500 staff across the UK, is owned by Japan-based firm NSG.